Various approaches to making a chair's seat and back form fitting for various users are known in the industries of seating manufacture. These approaches range from the rather traditional use of contouring synthetic foam, to seat/back shells that have a degree of flex. There have also been approaches that use a frame that has a membrane or sling stretched or supported within said frame. Several problems exist with each of these approaches.
In the case of simply using foam padding, under normal manufacturing conditions it is difficult if not impossible to properly vary the amount of firmness and thus support from one area of a cushion to another. Additionally, having to use foam can lead to excessive heat-build-up between the seating surface and the occupant. One of the problems with foam is the forming/molding of it. Current manufacturing technology makes it a relatively inefficient process compared with the manufacture of the other components that make up a chair of seating surface. The forming/molding of a contoured seating surface is so slow that the manufacturer is forced to make many sets of molds (which usually are hand filled) in order to maintain the production pace. This is contrasted by a part or component that is made for the same piece of furniture yet it can be produced on a single injection-molding machine with a single mold and keep pace. Another problem inherent to the use of foam is that in order to achieve a finished look the cushions must be upholstered. When a manufacturer is forced to upholster a cushion a number of problem issues arise. Usually the formed or molded foam has curves, many of which can be compound-curves, which leads a manufacturer to use glue or other adhesives to make the fabric conform to the contours. This laminating technique often makes the foam's surface firmer than it was when it was originally molded/formed because the glue/adhesive and the fabric are now part of the foam structure. Additionally, the amount of change can vary from fabric to fabric which results in an unpredictability of the firmness of a cushion from one manufactured unit to the next. If a slipcover is used, it must be sized properly. Such sizing can be difficult as a result of the differing mechanical properties found from one fabric to another. The most important properties of a fabric when upholstering a contoured surface are its thickness and its rate of stretch. Thickness variations can make one fabric upholster smooth around radii or contours, while a thicker one will wrinkle in the same area. Variations in the amount of stretch can lead to other problems. And so a proper size slipcover in one type of fabric, with its stretch characteristics, can be the wrong size in another type or style of fabric. Often a manufacturer will “wrap” a piece of fabric around a cushion and then staple the fabric to the underside/backside of the cushion. This approach also suffers from the aforementioned problems associated with using variable fabrics. Additionally, The manufacturer must now cover the staples and the area of the cushion not covered by fabric in order to achieve a finished look. This leads to an additional molding etc. that often also has to be upholstered.
The other reality of cushion upholstery, regardless of the techniques used, is that whether it is done in a small shop or in a production situation, it is consistently the most labor-intensive aspect of chair/seating construction.
In the case of incorporating flex into the shells of a chair, no geometry to date has achieved the proper amount of flex in the right areas to give correct ergonomic comfort for a wide range of individuals. In the case of a sling approach, the curves imparted on the sling by the frame are simple in nature (non-compound) and thus cannot provide the proper contouring necessary for ergonomic comfort. Also, this approach leads to “hammocking”. Hammocking is when the sling is pressed in one area; the areas immediately adjacent have the tendency of folding inward, squeezing the occupant, again not yielding the proper ergonomic curvatures. An additional problem with sling chairs is that if the manufacturer makes the supporting sling surface taut enough to properly support a large-heavy person, the tension on the sling will be too great for a smaller person, resulting in discomfort.
Finally, the present state of the art dictates that the contours a designer may choose in seating design be generic in nature to accommodate the widest range of the population possible. In an effort to increase comfort, manufacturers have produced “sized” (i.e. small, medium and large) chairs that effectively narrow the amount of contouring-compromise that the designer must normally exercise. Unfortunately, this leads to the manufacturer having to tool three independent products instead of one, and the manufacturers, wholesalers, and retailers having to stock (in this example) three times the quantity of product. Additionally, the end user is stuck with a chair that at some point in the future may be the wrong size. This invention addresses these shortcomings with a new and novel approach to seating construction.